Re: [Qemu-devel] [PATCH v2 4/7] scripts/qemu.py: set predefined machine type based on arch

[Philippe Mathieu-Daudé]

On 10/10/2018 01:26, Cleber Rosa wrote:
> Some targets require a machine type to be set, as there's no default
> (aarch64 is one example).  To give a consistent interface to users of
> this API, this changes set_machine() so that a predefined default can
> be used, if one is not given.  The approach used is exactly the same
> with the console device type.
> 
> Also, even when there's a default machine type, for some purposes,
> testing included, it's better if outside code is explicit about the
> machine type, instead of relying on whatever is set internally.
> 
> Signed-off-by: Cleber Rosa <address@hidden>
> ---
>  scripts/qemu.py | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/qemu.py b/scripts/qemu.py
> index d9e24a0c1a..fca9b76990 100644
> --- a/scripts/qemu.py
> +++ b/scripts/qemu.py
> @@ -36,6 +36,15 @@ CONSOLE_DEV_TYPES = {
>      r'^s390-ccw-virtio.*': 'sclpconsole',
>      }
>  
> +#: Maps archictures to the preferred machine type
> +MACHINE_TYPES = {
> +    r'^aarch64$': 'virt',
> +    r'^ppc$': 'g3beige',
> +    r'^ppc64$': 'pseries',
> +    r'^s390x$': 's390-ccw-virtio',
> +    r'^x86_64$': 'q35',

Why choose Q35 rather than PC (the default)?

I was wondering about how to generate variants/machines.json but this is
definitively something we want to do via a QMP query.

Eduardo what do you think?

> +    }
> +
>  
>  class QEMUMachineError(Exception):
>      """
> @@ -413,13 +422,24 @@ class QEMUMachine(object):
>          """
>          self._arch = arch
>  
> -    def set_machine(self, machine_type):
> +    def set_machine(self, machine_type=None):
>          '''
>          Sets the machine type
>  
>          If set, the machine type will be added to the base arguments
>          of the resulting QEMU command line.
>          '''
> +        if machine_type is None:
> +            if self._arch is None:
> +                raise QEMUMachineError("Can not set a default machine type: "
> +                                       "QEMU instance without a defined 
> arch")
> +            for regex, machine in MACHINE_TYPES.items():
> +                if re.match(regex, self._arch):
> +                    machine_type = machine
> +                    break
> +            if machine_type is None:
> +                raise QEMUMachineError("Can not set a machine type: no "
> +                                       "matching machine type definition")
>          self._machine = machine_type
>  
>      def set_console(self, device_type=None):
>